The present invention relates to high refractive index, reinforced compositions, and to lens bodies made from such compositions. More particularly, the invention relates to reinforced compositions which have an advantageous combination of properties, including high index of refraction and strength, which are useful in lenses, such as intraocular lenses.
Intraocular lenses (IOLs) have been known for a long time. Such lenses are surgically implanted into the human eye to replace damaged or diseased lenses of the eye.
Whereas IOLs can be made from "hard" polymeric or glass optical materials, soft resilient polymeric materials comprising polysiloxane polymers or copolymers have been increasingly used in the art for this purpose.
IOLs made from silicone polymeric materials are preferably deformable, so that for implantation a smaller incision needs to be surgically cut in the eye than for the implantation of "hard" IOLs. In this respect, the size and mechanical characteristics of the silicone polymeric IOLs play an important role. As it will be well understood by those skilled in the art, for successful implantation the lens must have sufficient structural integrity, strength, elasticity and elongation and small enough size to permit the folding for insertion through a small incision. After insertion, the lens must, of course, regain its original molded shape and have sufficient structural integrity and strength to retain such shape under normal use conditions.
It will be further understood by those skilled in the art that the thinner is the lens, the easier is the surgical insertion procedure. On the other hand, in order to function as an IOL, the lens material must have sufficient optical refractory power. Consequently, the higher is the optical refractive index or index of refraction of the silicone material, the thinner can be the lens to obtain the same optical refractory power.
Some silicone polymeric materials described in the prior art include a reinforcer. Usually such reinforcement of the silicone polymeric material is necessary for the polymeric material to attain adequate structural strength to be used as a foldable IOL. Examples of reinforced silicone polymeric materials suitable for use as soft contact lenses or IOLs are described in U.S. Pat. Nos. 3,996,187 and 3,996,189.
Travnicek U.S. Pat. No. 3,996,189 discloses that the inclusion of diphenyl siloxane or phenyl-methyl siloxane into a polysiloxane increases the refractive index of the composition. This patent discloses silica as a reinforcer or filler component to increase the strength of the composition. Further, this patent discloses that the silicone copolymer has essentially the same refractive index or index of refraction as the silica filler to form a transparent, optically clear contact lens. The silicas useful as strength reinforcers for such elastomers have limited indexes of refraction, being no greater than 1.46. Thus, if it is desired to form an optically clear silicone elastomer-based lens, the elastomer may have to have an index of refraction of 1.46 or less, or may require that no reinforcer component be included. Because of the advantages of high refractive index materials, it would be advantageous to provide an optically clear silicone polymer-based composition with sufficient strength, for example, to be used in lenses and lens bodies.